This invention relates to liquid cleansing compositions, in particular liquid cleansing products which are high foaming and have a high degree of mildness.
In recent years, it has increasingly become a desirable attribute of commercially available cleansing products, in particular those products for personal washing, that such products combine a rapid and abundant lather with improved mildness, in order to minimise skin damage.
It is well known that anionic surfactants confer lathering properties to compositions in which they are contained. A previously used approach to improving the mildness of compositions containing anionic surfactants has been to partially replace the anionic surfactants with a suitable coactive surfactant, which is typically an amphoteric and/or a nonionic surfactant. Without being bound by theory, it is thought that this partial replacement of the anionic surfactant in the composition serves to reduce the critical micellar concentration of the anionic surfactant composition, and thereby reduce its harshness.
A further approach to ameliorating the harshness of anionic surfactant containing compositions has been to include in the composition one or more hydrophobic and emollient materials, such as for example silicone oils, mineral oils or cholesterol. The addition of such hydrophobic materials has generally proved successful in enhancing the mildness of the cleansing composition, but with a tendency to consequently reduce the amount of lather that they produce in use, because of their hydrophobic nature.
In addition, a farther problem encountered is that cleansing compositions general have a tendency to be susceptible to bacterial and microbial gradation; this is unacceptable for any product which is to be applied to e skin for the purposes of washing or cleansing. Hence, with such products, usually a necessary component of the composition is a suitable organic anti-bacterial and/or anti-microbial agent. Typical examples of anti-microbial and/or anti-bacterial agents which are commercially available include those under the trade names Kathon CG (ex Rohm and Hass), Phenoxyethanol (ex Nipa Laboratories), Parabens (ex Nipa laboratories), Germall 11 (ex ISP) and Glydant plus (ex Lonza), as well as materials such as formaldehyde.
However, a disadvantage of incorporating such organic anti-bacterial and/or anti-microbial compositions into a personal wash composition is that these materials can provoke adverse skin reactions. This is thought to be due to their mode of action, and therefore their levels in the commercial product must be minimised. In addition, a number of anti-bacterial and/or anti-microbial agents are suspected of toxicity.
It would therefore be highly advantageous to manufacture a personal wash composition which has good lathering properties and enhanced mildness, whilst at the same time is devoid of any recognised organic anti-bacterial and/or anti-microbial agents, but which nevertheless possessed anti-microbial and/or antibacterial properties.
We have surprisingly found that it is possible to provide liquid personal wash compositions which have high levels of lather generation and very good levels of mildness, but which are absent any recognised organic anti-microbial and/or anti-bacterial agents. Thus, according to a first aspect of the invention, there is provided a personal wash liquid composition which comprises 10 to 40% of one or more anionic surfactants, 30 to 50% of one or more humectants, and less than 55% water, characterised in that the water activity of the product is less than 0.9.
Conveniently, compositions according to the invention are free of any anti-microbial and/or anti-bacterial agents.
Compositions according to the invention preferably contain at least 10% water. Compositions are also ideally not encapsulated.
Compositions according to the invention comprise relatively high levels of humectants, which preferably are polyol humectants. Examples of suitable humectants include glycerol, sorbitol, polyethylene glycol, and mono- and oligomeric sugars. A particularly preferred humectant is glycerol. Although not wishing to be bound by theory, it is believed that compositions according to the invention can exist satisfactorily without the use of conventional anti-microbial and/or anti-bacterial agents, because of the relatively low maximum water activity of the compositions. In particular, an upper level of water activity of 0.9 has been found, at which level or below cosmetic compositions according to the invention are xe2x80x9cself preservingxe2x80x9d.
In the context of the invention, the xe2x80x9cwater activityxe2x80x9d (a) of the composition is defined as a=p/po, where p is the measured partial pressure of the solution and po is the partial pressure of distilled deionised water. Unless stated otherwise, all water activities are quoted are at ambient temperature. Further references to water activity (or relative humidity, where relative humidity (RH)=100 a) can be found in Morris, C. and Leech, R., xe2x80x9cNatural and Physical Preservative Systemsxe2x80x9d, Curry, J. xe2x80x9cWater Activities and Preservativesxe2x80x9d, Cosmet. Toilet. 100, 53-55, and Christian, J. H. B., xe2x80x9cReduced Water Activityxe2x80x9d. In:Silliker, J. H. (ed) xe2x80x9cMicrobial ecology of Foodsxe2x80x9d, vol. 1, Academic Press, New York, pp170-192.
In addition to the relatively low water activity that the high levels of humectants provide in topical compositions, we have surprisingly found that relatively high levels of humectants do not negatively affect the lathering or sensorial properties of the topical compositions. They can however contribute positively to the mildness of the product.
Compositions according to the invention have a water activity of less than 0.9, preferably less than 0.87, more preferably less than 0.85, and even more preferably less than 0.81.
Cosmetic compositions according to the invention comprise a surfactant component which itself contains an anionic surfactant. The surfactant component contained in the composition may be any combination of surfactants, provided that it comprises an anionic surfactant, and that it provides the composition with a suitable level of foaming. As such, the surfactant component of the composition may comprise in addition to anionic surfactants soaps, cationic, nonionic, zwitterionic and amphoteric surfactants, and mixtures thereof.
Suitable soaps include these having carbon chain lengths of C8-C24, be saturated or unsaturated, and have any appropriate cation, such as sodium, potassium, ammonium or triethylammonium.
The composition according to the invention comprises an anionic surfactant, which may preferably be chosen from alkyl sulphates, alkyl ether sulphates, alkyl sulphonates, alkyl aryl sulphonates, olefin sulphonates, acyl sarcosinates, acyl taurides, acyl isethionates, nonoalkyl sulphosuccinates, dialkylsulphosuccinates, N-acylated xcex1-amino acids, alkyl carboxylates, monoalkyl phosphates and dialkyl phosphates, and mixtures thereof. Specific examples of suitable anionic surfactants include:
alkyl sulphates, such as sodium lauryl sulphate [eg EMPICOL CX available from Albright and Wilson], and triethanolaminde lauryl sulphate [eg EMPICOL TL40/T, available from Albright and Wilson];
alkylether sulphates, such as sodium lauryl ether sulphate [eg EMPICOL ESB70, available from Albright and Wilson];
alkyl sulphonates, such as sodium alkane (C13-18) sulphonate [eg HOSTAPUR SAS 30, available from Hoechst];
alkylaryl sulphonates, such as sodium alkyl benzene sulphonate [eg TEEPOL CM44, available from Shell];
olefin sulphonates, such as sodium olefin sulphonate (C5-18) [eg HOSTAPUR OS, available from Hoechst];
acyl sarcosinates, having the structure: (51) 
where
R3 is chosen from C6-14 alkyl, and
M is a counterion chosen from alkali metals, ammonium and substituted ammonium such as alkanolammonium.
An example of an acyl sarcosinate having the structure (51), is sodium lauryl sarcosinate [eg HAMPSOYL L-95, available from Grace].
acyl taurides, having the structure (52): 
wherein R4 is chosen from C8-18 alkyl;
An example of an acyl tauride having the structure (52) is coconut methyl taurine [eg FENOPEN TC 42, available from International Specialty Products].
acyl isethionates, having the structure (53): 
wherein R5 is chosen from C8-18 alkyl;
An example of an acyl isethionate having the structure (53) is sodium acyl isethionate [eg JORDAPON C1, available from Jordon].
monoalkyl sulphosuccinates, having the structure (54): 
where R6 is chosen from C10-20 alkyl.
Examples of monoalkyl sulphosuccinates having the structure (54) include:
sodium lauryl sulphosuccinate [eg EMPICOL SLL, available from Albright and Wilson];
magnesium alkyl sulphosuccinate [eg ELFANOL 616 Mg, available from Akzo];
sodium lauryl ethoxysulphosuccinate [eg EMPICOL SDD, available from Albright and Wilson];
coconut monoethanolamide ethoxysulphosuccinate [eg EMPICOL SGG];
disodium lauryl polyglycolether sulphosuccinate [eg SURTAGENE S30, available from CHEM-Y];
polyethyleneglycol sulphosuccinate [eg REWOPOL SBFA 30, available from REWO];
dialkyl sulphosuccinates, having the structure (55): 
where R7 and R8 are the same or different, and are chosen from C6-14 alkyl.
An example of a dialkyl sulphosucciante having the structure (55) is sodium dilauryl sulphosuccinate [eg EMCOL 4500, available from Witco];
N-acylated amino acids, such as sodium lauroyl glutamate [eg AMISOFT LS-11 (F), available from Ajinomoto Co Inc], potassium cocoglutamate [e.g. AMISOFT CK11, available from Ajinomoto Co Inc], potassium cocoglycinate [e.g. AMILITE GCK 11F] and potassium cocosarcosinate.
alkyl ether carboxylates, such as C12-14O(EO)4OCH2CO2Na [eg AKYPO RLM 38, available from Akzo];
monoalkyl phospates and dialkyl phospates, such as dioctyl phosphate;
Further examples of anionic surfactants (and of the other types of surfactants) are described in xe2x80x9cSurface Active Agents and Detergentsxe2x80x9d (vols. I and II), by Schwartz, Ferry and Bergh. Preferred anionic surfactants include aminocarboxylate surfactants.
In certain embodiments, preferred anionic surfactants include alkyl ether sulphates, fatty acid soaps, alkyl sulphates, alkyl sulponates, isethionic acid derivatives, and mixtures thereof. In certain embodiments, preferred non-soap anionic surfactants may be C8-C22 alkyl unsubstituted isethionates.
The composition of the invention can also comprise an amphoteric surfactant. Suitable amphoteric surfactants are derivatives of aliphatic quaternary ammonium, phosphonium and sulphonium compounds, wherein the aliphatic radicals contain from 8 to 18 carbon atoms, and may be straight chain or branched, and further contain an anionic water solubilising group, such as carboxyl, sulphonate, sulphate, phosphate or phosphonate.
Preferred amphoteric surfactants include:
Alkyl betaines, having the structure (58): 
where R1 is C1-16 alkyl.
An example of an alkyl betaine having the structure (58) is lauryldimethyl betaine [eg EMPIGEN BB, available from Albright and Wilson].
alkylamidopropyl betaines, having the structure (59): 
An example of an alkylamidopropyl betaine having the structure (59) is cocamidopropyl betaine (eg TEGOBETAIN L7, available from Goldschmidt);
alkylamphoglycinates or Alkylamphopropionates having the structure (60): 
where R11 is chosen from H, CH2COOxe2x88x92 and (CH2)2COOxe2x88x92, and R111 is chosen from CH2COOxe2x88x92 and (CH2)2COOxe2x88x92.
Suitable examples of compounds (60) are cocoamphoglycinate (available from International Specialty Products), and cocoamphopropionate;
sultaines, having the structure (61): 
where R2 is chosen from C12-16 alkyl alkylamido groups.
An example of a sultaine having the structure (61) is cocamidopropylhydroxysultaine [eg CYCLOTERIC BET-CS, available from Alcolac).
A further suitable amphoteric surfactant is a cocamidopropyl trimethyl ammonium chloride, such as Empigen CSC, available from Albright and Wilson.
The most preferred amphoteric surfactants are lauryl dimethyl betaine and cocamidopropyl betaine. Such amphoteric surfactants can contribute to the foaming of the skin cleansing composition, while ameliorating the harshness of the anionic surfactant.
The composition of the invention can also comprise a nonionic surfactant. Suitable nonionic surfactants include polyoxyethylene alkyl esters, polyoxyethylene alkyl ethers, and alkyl polyglycosides.
A suitable example of a polyoxyethylene alkyl esters is that having the CTFA designation Polysorbate 80 which is a mixture of oleate esters of sorbitol and sorbitol anhydrides, condensed with approximately 20 moles of ethylene oxide. Also suitable is Polysorbate 20 which is a mixture of laurate esters or sorbitol and sorbitol anhydrides condensed with approximately 20 moles of ethylene oxide.
Polysorbate 80 and Polysorbate 20 are available commercially as TWEEN 80 and TWEEN 20 respectively, from ICI Americas.
Also suitable for use in the compositions of the invention is the polyethylene glycol ether of C9-11 alcohol with an average of 8 ethoxy units, which is available commercially as NONIDET LE-8T or as SYNPERIONIC 91-8T, and the polyethylene glycol ether of C12-15 alcohol with an average of 9 ethoxy units which is available commercially as DOBANOL 25-9.
Particularly useful alkyl polyglycosides include the glycosides of glucose or glucose oligomers where the alkyl chain can be C8-16 and the average number of glucose units is 1 to 2. A suitable example is ORAMIX NS 10, which is the glucoside of C10-12 fatty alcohol with an average of about 1.5 glucose units.
Conveniently, the total level of surfactant present in the composition is a level of 10-50% by weight. Preferably the total level of surfactant in the composition is at least 12% by weight; preferably, the level of surfactant in the composition is less than 35% by weight. The anionic component of the surfactant content of the composition can typically be 40-100% of the total surfactant content of the composition.
Preferably, the ratio of anionic surfactants to co-surfactants (ie amphoteric and/or nonionic surfactant) is greater than or equal to 1:1.
The invention will now be further described by way of example only.